Flavonoid and proanthocyanidin polymers having a varying number of flavonoid units are known and have been reported, for example, in W. L. Mattice, et al., Phytochemistry, 23, p. 1309-1311 (1984); Z. Czochanska, et al., J. C. S. Chem. Comm., 375 (1979); W. T. Jones, et al., Photochemistry, 15, p. 1407-1409 (1976); E. Haslam, Plant Polyphenols, p. 75 (1989). Compounds such as proanthocyanidin polymers have been previously described as having anti-viral activity. See, e.g. International Publication Number WO/92/06695 to Shaman Pharmaceuticals, Inc. and International Publication Number WO 90/13304 to Cariel et al. These compounds have been extracted from various plant materials such as Croton and Calophyllum plant species.